1. Field of the Invention
This invention relates to sound barrier mats and, more particularly, to dash mats for vehicles having integrally molded hinged doors for installing vehicle accessories.
2. Description of the Related Art
In most contemporary automobiles, a steel firewall separates the engine compartment from the passenger compartment. To reduce the transmission of sound from the engine compartment through the firewall and into the passenger compartment, a sound barrier mat (otherwise known as a dash mat) is typically molded of an elastomeric material. The dash mat is mounted to and substantially overlies the firewall such that an outer surface of the mat is in contact with a bottom surface of the vehicle carpet and extends beyond the carpet to an upper portion of the firewall behind the instrument panel. The dash mat is typically spaced from the firewall by an absorber layer that is usually constructed of an open cell foam or fiberglass material.
Multiple apertures are formed in the dash mat for receiving a corresponding number of mounting studs that project from the firewall for securing the dash mat thereto. Other apertures in the dash mat are aligned with openings in the firewall for the passage of cable guides, wiring harnesses, steering columns, accessory mounts, and so on. Certain vehicle accessories are typically mounted before dash mat installation while other accessories are mounted thereafter. The installation of a wiring harness that extends through an aperture in the dash mat is normally a difficult task. A typical vehicle wiring harness includes several wires wrapped together to form a cable. One or more of the wires may terminate in an electrical plug that is larger than the diameter of the cable, and several electrical plugs may be provided in a single wiring harness. Since the dash mat is designed to insulate the passenger compartment from the engine compartment, the wiring harness aperture in the dash mat must be sized to fit snugly around the cable. However, since the electrical plugs are larger than the diameter of the cable, it is difficult to install the plugs through the wiring harness aperture without damaging the dash mat, the plugs, or the electrical connection between the wires and plugs. To avoid possible damage, a slit typically extends from an edge of the dash mat to the wiring harness aperture. Although the slit facilitates installation of the wiring harness, the aperture and slit impair the sound reduction qualities of the dash mat.